Field of the Invention
Aspects of the present invention relate to a method for manufacturing a glass material by using a containerless melting method and a method for manufacturing a lens. In addition, aspects of the present invention relate to a melting apparatus.
Description of the Related Art
The containerless melting method is a manufacturing method in which a material is melted and solidified without using a container. With this method it is possible to avoid nucleation at a solid-liquid interface and thereby avoid part of the materials not being vitrified by a manufacturing method in which a container is used. Consequently, the containerless melting method is expected, as a method for manufacturing a glass material, to have heretofore unrealized new characteristics.
In the containerless melting method, a raw material is levitated and, thereby, has no contact with the surroundings. Examples of levitation methods include an electrostatic levitation system, an acoustic levitation system, an electromagnetic levitation system, and an aerodynamic levitation system. Among them, the aerodynamic levitation system is promising as a system capable of establishing the noncontact state in a relatively stable way without requiring complicated equipment.
The aerodynamic levitation system is a technique to levitate a material, which has been melted with a heating unit so as to become a viscous body, above a furnace by the force of a gas stream, and control of the levitation behavior of the material is an important issue. In particular, in the case where a large volume of glass is produced, the difficulty associated with the control increases. In order to deal with such an issue, Japanese Patent laid-Open No. 2014-141389 proposes a glass manufacturing method, in which a furnace having a plurality of gas ejection holes in the vertical direction is used, based on a containerless melting method.
However, according to the glass manufacturing method described in Japanese Patent laid-Open No. 2014-141389, as the volume of glass to be produced increases, contact between the levitated glass material and the furnace occurs easily.